From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BF0DC39D6EF for ; Mon, 10 Aug 2026 07:12:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.197 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786345974; cv=none; b=SfL5EJzuauY0dUncdARljJNI6Q1L6AWsinL/F+JU6imMT/25jYLUI502U1UA1zHbI8DpikUjo2NkC9b28gWp6OoYACXU0uSzxowYfmCK+yQpEYxOhlqvfEpzXtgqL7qN/xBKt9iWCHfzy3J5BLDO2foiwJgPG1N6GRC3fOGZpwc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786345974; c=relaxed/simple; bh=xQQ324yJppjYXSfwfG7HdtFxsh6X7PGSrguVedWo/tg=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=M8B9gMjaO8EDexiON+DiRBeBjczVvqgta2J3/anLyTh1Iff/cgdzctjdcYnmX45tY5iwq4iehdEnEa8uQ1iwA9D96WhPZ+brGXlnt+XxJGMjFnZSrwotQqJWUDnOLxwaYLhXTYJF7hAZm2Bjrw5KVeqU0DRWpsmJ0xFNuVTHvNs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--sonalipradhan.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=nYP9oQqW; arc=none smtp.client-ip=209.85.210.197 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--sonalipradhan.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="nYP9oQqW" Received: by mail-pf1-f197.google.com with SMTP id d2e1a72fcca58-8488ac68185so4450379b3a.2 for ; Mon, 10 Aug 2026 00:12:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1786345972; x=1786950772; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=y+mjXAOsh87MLiqe7Al+hJ0jHWJBBARtP7EOkjQ8zvc=; b=nYP9oQqWq0xkWvi0DzvgIgX3JIsQ1eWQjBQV7qHtT6iMDaVEZYJRK3hA/5wHFQNcsS qBia91wH6/MVFdHocH4v0jX6Ywx6ZfeWLwx35JSUEKP5JypmzUOrnlbLEUa+uJDUYk8G dtaw9SKRstcJQOMFHHBElcHopdUDy5bnR5o2h154dAwrsDLzVNeZNzRMfvK/0paPH6Mu nYyMPdoiHXLgKfLspgn6NgFnuMtDKX8Em0pU3lJszF0NQ9ozrG1vIBXhi3ooxUDznodB Ermlin+dGVK8haee4V/UN00aQ/iA4C3KQxCOfwrIaethG3lqTsNX0l271ElG3vbeEIIg udUA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786345972; x=1786950772; h=content-type:cc:to:from:subject:message-id:mime-version:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=y+mjXAOsh87MLiqe7Al+hJ0jHWJBBARtP7EOkjQ8zvc=; b=T3v5L36zvCwQtBVvCKpFEOXOgIBii3tXcq5cU5y5JcLHod5Zw+k0KmAzoJMoYLVh/k QFQI/yfBQQw2OUzQZBPKNY8PJvIdiC2SPV6ZuvVSqUPPO+uOwqsDdg3PR6Jas3f+umzj /MU2YJrwd0DvSJMxenOEkXi7dZbmm1vJkoui+C+ZJXeyhkxuEyJ/Q91oAedVE1a6GHmB yG4Pzja58weh2XZfeYHC+RoVWYLpifWTT9mEcykuUMXKHT+41XXyZKJjC8UIBEkNkmDQ CwKpVicPd2GW2syJpj1Gv4vetEuOvfFo4hg8Oq0O+EOlsIdL3em+2/dEquAuMN/UwjPV LzPQ== X-Forwarded-Encrypted: i=1; AHgh+RoAFOGeqV4HEFRA88LNY/T6sLMX3RaQ0nJxZkVi57iHre1jKqOlT7287F9Bekn8pArvDqPXuVwfsAeCyGo=@vger.kernel.org X-Gm-Message-State: AOJu0YzPND2i9yCbocrpXd34O5zYBFxPh3Ltq7IZ/qQ3a5SgOs77Sw8r 2cwW4Kb3iX4loZgyblXmHUotqByvGeBC1iB9HnViefrnml2Rr9+Fi/zYjKPguy3mW6ZIViIWJvO 9xYCnGWKX/+GlCQP498dhcGqNrOZy9RSnig== X-Received: from pfbeb25.prod.google.com ([2002:a05:6a00:4c99:b0:848:49f6:6f5c]) (user=sonalipradhan job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:848:b0:84c:3900:95d4 with SMTP id d2e1a72fcca58-84f694915ccmr17354002b3a.11.1786345971760; Mon, 10 Aug 2026 00:12:51 -0700 (PDT) Date: Mon, 10 Aug 2026 07:12:37 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.55.0.654.g21b8a5bc05-goog Message-ID: <20260810071237.2207680-1-sonalipradhan@google.com> Subject: [PATCH] usb: gadget: u_audio: Fix use-after-free on sound card disconnect From: Sonali Pradhan To: Greg Kroah-Hartman Cc: Kees Cook , Xu Rao , "=?UTF-8?q?Alvin=20=C5=A0ipraga?=" , John Keeping , Ruslan Bilovol , stable@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Sonali Pradhan Content-Type: text/plain; charset="UTF-8" g_audio_cleanup() invokes snd_card_free_when_closed() to initiate sound card teardown and immediately frees the underlying struct snd_uac_chip context. However, snd_card_free_when_closed() returns asynchronously while ALSA control elements (kctls) remain open in userspace. When userspace control applications access or close these open file descriptors, kctl callbacks attempt to dereference kctl->private_data pointing to &uac->c_prm or &uac->p_prm within the freed uac structure, resulting in a use-after-free (UAF) memory corruption. Fix this issue by deferring the destruction of struct snd_uac_chip until all references to the ALSA sound card are released. Register a custom card->private_free callback (u_audio_card_free) during g_audio_setup() that frees uac and its associated playback/capture request and ring buffers only when the sound card reference count drops to zero. Fixes: 6c67ed9ad9b8 ("usb: gadget: u_audio: don't let userspace block driver unbind") Cc: stable@vger.kernel.org Signed-off-by: Sonali Pradhan --- drivers/usb/gadget/function/u_audio.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c index ca26bf9c8040..f0ee83abcebc 100644 --- a/drivers/usb/gadget/function/u_audio.c +++ b/drivers/usb/gadget/function/u_audio.c @@ -1183,6 +1183,20 @@ static struct snd_kcontrol_new u_audio_controls[] = { }, }; +static void u_audio_card_free(struct snd_card *card) +{ + struct snd_uac_chip *uac = card->private_data; + + if (!uac) + return; + + kfree(uac->p_prm.reqs); + kfree(uac->c_prm.reqs); + kfree(uac->p_prm.rbuf); + kfree(uac->c_prm.rbuf); + kfree(uac); +} + int g_audio_setup(struct g_audio *g_audio, const char *pcm_name, const char *card_name) { @@ -1262,6 +1276,8 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name, goto fail; uac->card = card; + card->private_data = uac; + card->private_free = u_audio_card_free; /* * Create first PCM device @@ -1430,6 +1446,8 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name, snd_fail: snd_card_free(card); + return err; + fail: kfree(uac->p_prm.reqs); kfree(uac->c_prm.reqs); @@ -1455,12 +1473,6 @@ void g_audio_cleanup(struct g_audio *g_audio) card = uac->card; if (card) snd_card_free_when_closed(card); - - kfree(uac->p_prm.reqs); - kfree(uac->c_prm.reqs); - kfree(uac->p_prm.rbuf); - kfree(uac->c_prm.rbuf); - kfree(uac); } EXPORT_SYMBOL_GPL(g_audio_cleanup); -- 2.55.0.654.g21b8a5bc05-goog